The invention relates to a method for supplying ink to an ink tray of a printing press, wherein the ink consumption of the ink zones of the printing area is determined, the so determined data is sent to a computer, processed in the computer and control signals for the zonal ink supply are provided to the single ink zones according to the local ink consumption. The invention also relates to an apparatus for supplying ink to an ink tray of a printing press, wherein a stationary ink supply device is allocated to the ink tray and is controlled by a computer, and an ink ball extending over the entire width of the printing area and allocated to the ink tray establishing a dosing gap with an ink blade, which is separated into multiple ink zones.
An apparatus to establish a constant ink level in ink trays of printing presses is known from German patent No. 2,324,462. The constant ink level is sought to keep at a low level the printing ink volume in the ink tray. For this purpose an ink agitator is used, traversing along the ink ball is used. The movement creates a wave which is sensed by a sensor traveling above the ink agitator as a gauge for the ink level. If the ink level is exceeding a preset level the ink supply is stopped.
This solution was stated to guarantee a constant low ink level in the ink tray. It is, however, not possible to supply the ink to particular ink zones according to the ink consumption requirements.
This problem is stated to be solved by German patent No. 19,512,727 by providing an ink cartridge that is movable on a slide. A traveling sensor is allocated in the direction of motion before the ink cartridge to detect the zonal ink level in the various ink zones. The sensor sends a control signal if the ink level is too low. This causes the release of an appropriate amount of ink from the ink cartridge to the ink zone that is in need for more ink.
The latter structure has the disadvantage that the supplied fresh inkplaced on top of the already existing ink in supply the ink zones and therefore fresh and old ink become mixed, causing printing with ink of varying rheological properties.
It is an object of the present invention to provide a method and apparatus for zonal ink dosage according to the ink requirements, whereby the ink already in the ink tray and supplied fresh ink are intensively mixed with each other.
It is also an object of the present invention to provide a method and apparatus for zonal ink dosage according to ink requirements with an intensive mixing of ink already in the ink tray and fresh supplied ink.
These objects are solved according to the present invention by a zonal ink supply to the ink zones in supply cycles, whereby the required amount of ink for the ink zones is supplied by a fixed ink supply device and shifted by an ink spatula from this supply location to the ink needing ink zones.
It is an advantage of the solution according to the present invention that the ink has the same rheological properties over the entire width of the ink tray. An ink profile according to demand is kept over the entire width of the ink tray during the whole printing process. The ink tray always carries a minimum amount of ink, so that only small amount of ink remains in the ink tray at the end of a printing job.